1.First, we tried to developed postherpetic neuralgia rat model reported by Kuraishi. However, this model was criticized because of injection of herpes simplex virus. Then, we tried to develop a new postherpetic neuralgia rat model, but this herpes zoster virus was impossible to acquire. Therefore, we changed target to other neuropathic pain models.2.We measured the mRNAs of cyclooxygenase(COX)-2, and trkB receptor in the spinal cord, and also brain-derived neurotrophic factor(BDNF) in the dorsal root ganglion(DRG) after an injection of formalin in the hind paw of a rat with L5 spinal nerve ligation(SNL)-induced neuropathy. We also measured c-fos mRNA expression in the spinal cord to clarify changes in neuronal activities in the central pathways. c-fos study indicates that the decrease in neuronal activities to inflammation pain in the spinal cord after SNL-induced neuropathy may play an important role in changing in the perception of acute pain. Increase in mRNA of BDNF after SNL-induced neuropathy suggests that overexpression of BDNF in the spinal cord could alleviate formalin-induced pain.3.We established the real-time PCR method to quantify mRNA in the spinal level. Consequently, we became able to quantify a very small amount of neurotrophic factors. Furthermore, we got a technique of in situ hybridization and intrathecal administration of drugs. Antisense RNA of neurotrophic factors could be administered intrathecally in the neuropathic pain model.